BIOLOGICAL PHOSPHORUS REMOVAL AT STRATFORD-UPON-AVON, UK - THE EFFECTOF INFLUENT WASTE-WATER CHARACTERISTICS ON EFFLUENT PHOSPHATE

Severn Trent as part of their wastewater development strategy have bui lt a Full scale biological nutrient removal plant at Stratford-upon-Av on, where Mainstream and Sidestream Phostrip(R) processes are studied. The plant, designed to treat 5000 m(3)/d, was commissioned in Novembe r 1993 and whilst the Phostrip(R) plant has consistently achieved the target level of 1 mg/l P, the UCT plant is able to achieve this standa rd only with the addition of fermenter liquor containing sufficient co ncentrations of Short Chain Fatty Acids (SCFA). Enforced decommissioni ng of the sludge fermenter provided an interesting period of study whe n both the anaerobic phosphorus release and aerobic phosphorus uptake deteriorated as the concentration of combined phosphate in the polyP b iomass fell steadily to a level of less than 3% phosphorus. Effluent p erformance was restored following subsequent recommissioning of the sl udge fermenter and the authors conclude that the Stratford sewage, des pite having a BOD:P ratio greater than 20 and considered a strong sewa ge, still required the addition of SCFA for consistent phosphorus remo val. The authors conclude that SCFA addition to mainstream Enhanced Bi ological Phosphorus Removal Plants (EBPR) is required to maintain the poly P sludge in satisfactory condition to both release and uptake pho sphorus and meet the UWWTD standard of 1 mg/l P. Copyright (C) 1996 IA WQ. Published by Elsevier Science Ltd.